Structural, vibrational spectroscopic, and electrical conduction mechanisms of $\alpha$-NaCoPO4 compound

The orthophosphate alpha-NaCoPO4 compound was prepared from highly pure constituents with mechanical milling followed by heat treatment. X-ray diffraction data refined via Rietveld method revealed that this compound crystallizes in the orthorhombic system with Pnma space group. A thermal analysis shows that this composition undergoes one-phase transitions at Tþinspace=þinspace567 K. The infrared and Raman spectra confirm the presence of PO43− tetrahedral. The evolution of half-width $\Delta$$\nu$ and intensity report versus temperature introduces huge changes associated with the phase transition originating from the reorientation of the PO4 tetrahedra. Besides, the electrical data analysis of the impedance spectra is adapted to an equivalent circuit. Furthermore, the alternating current (AC) conductivity of grain contribution is interpreted using the Jonscher's universal power law. The AC conductivity behavior is ensured by a single process defined as a hopping transport mechanism. The conductivity frequency dependence is interpreted using the non-overlapping small polaron tunneling model (NSPT) in the two phases.